The field of the invention pertains to drink vending machines such as coffee machines or similar apparatus.
Certain drink vending machines use capsules containing ingredients to be extracted or to be dissolved; for other machines, the ingredients are stored and dosed automatically in the machine or else are added at the time of preparation of the drink. Most coffee machines also possess filling means comprising a pump for liquid, usually water, which pumps the liquid from a source of water that is cold or indeed heated through heating means, such as a heating resistor, a thermobloc or the like.
The fill of a drink in the receptacle, such as a cup or glass, is usually controlled in several different ways. In certain modes, the control of fill may be done by storing several fill programs in a controller which itself commands the time of activation of the pump and deactivates the pump via a relay. A drawback stems from the fact that depending on the state of the machine, for example the degree of limescale, the volumes actually delivered may vary significantly. As a consequence, the fill control is customarily done using a flow meter and by a control unit which counts down the number of pulses recorded on the flow meter positioned on the fluid supply circuit. However, a drawback is that it is necessary to provide a series of operating buttons depending on the number of different volumes to be delivered. For example, in a conventional coffee machine, a “ristretto” button is required for extra-short coffees (25 mL), an “espresso” button for short coffees (40 mL) and a “long” button for long coffees (110 mL). There is a real risk of confusion by the user unaccustomed to using the machine; this typically leads to the delivery of excessively strong coffees or to overspills from the cup. Another drawback arises from the lack of flexibility in respect of the user who may want an intermediate volume depending on the type of capsule or drink chosen. The flow meter may also lack accuracy or its accuracy be impaired on account of the scale which builds up on its surfaces. Another drawback arises from the fact that control by flow meter takes no account of the quantity of froth produced; this may lead to a spillover of froth for very frothy products.
Another mode consists in providing manual activation and deactivation of the pump by a button, a lever or some other operating means. Stated otherwise, the user alone is responsible for halting the flow of drink into the cup. However, this raises several drawbacks. One is that the user must remain attentive during the flow of the drink; without this, the system continues to deliver liquid: the risks of spillover are therefore fairly common. Another drawback arises from the fact that manual control such as this is inaccurate. The user may then encounter difficulties in reproducing the fill that he usually desires especially when the drink may produce more or less froth; this may fool the user in the control of the filling of the cup with liquid.
Another mode of control which is more complex and more expensive to implement consists of a means of recognition on a packaged portion of ingredients (for example, a capsule), such as a bar code, which transmits instructions to the machine, so as to tailor the volume to be delivered. In the same way, this system works on the activation of a pump using recorded programs and on the acquisition of data originating from a flow meter.
International patent application WO 97/25634 pertains to a method and a device for detecting the position of an object such as a container in a target window using the concept of triangulation of radiant energy. Such a device uses a first pair and a second pair of emitters and receiver and uses a triangulation calculation to detect the presence of the container. Such a device is not suitable for detecting the level of a drink in a receptacle.
U.S. Pat. No. 4,458,735 pertains to a device for automatically controlling the delivery of a drink such as a “milkshake” into a container made of translucent paper or foam. The receptacle is positioned under a source of radiation which directs a light ray against the rim of the receptacle; which ray passes through the receptacle and is detected by a radiation detector situated on the opposite side of the receptacle. The signal received by the detector is compared with a signal value level and when the attenuated signal drops below the signal value level, delivery is halted. Such a device does not allow sufficient detection accuracy, in particular, for coffee receptacles, on account of the way in which the incident signal is detected and then compared. Moreover, this device is unsuitable for translucent receptacles. Finally, the device does not make it possible to choose one's fill position. Thus, there is a need for improved devices of this type.